The following is a tabulation of some prior art that presently appears relevant: U.S. Patents
Pat. No.Kind CodeIssue DatePatentee8,100,461B2Jan. 24, 2012Smith et al.6,257,654B1Jul. 10, 2001Boivin et al.6,854,788B1Feb. 15, 2005Graham
Aerodynamicists have long known that box-type cargo trailers, of the type hauled by semi trucks, are aerodynamically inefficient. Their aft end in particular is a significant source of drag which adversely affects the fuel consumption of the hauling vehicle. These types of trailers are ubiquitous, however, because they are simple, inexpensive and offer the maximum cargo volume available within the dimensional limits set by state and federal transportation authorities. Thus, the challenge has been to design an economical aerodynamic structure for the aft end of existing cargo trailers that can be fielded unobstructively within the existing infrastructure of the cargo transport industry.
Several designs for rear-mounted aerodynamic fairings have been explored for existing cargo trailers with swinging rear doors. These fairings generally fall into two categories: “full” and “partial”. Full fairings, typified by U.S. Pat. No. 8,100,461 to Smith et al., are generally pyramidal in shape and provide fairing surfaces adjacent to the sides and the upper and lower surfaces of the trailer. Partial fairings, typified by one embodiment of U.S. Pat. No. 6,257,654 to Boivin et al., provide fairing surfaces adjacent only to the sides of the trailer.
Typically, full fairings are more aerodynamically effective than partial fairings, however, they also tend to be more complex. In order for a fairing to be operationally practical it must not interfere with the operation of the trailer doors. To this end, many full fairings are designed with actuation mechanisms which enable them to be swung, folded or otherwise collapsed into a less obstructive configuration when not in use. This added complexity results in higher manufacturing and maintenance costs and often saddles the trailer operator with the extra burden of deploying and stowing the fairing.
Partial fairings avoid much of the complexity of full fairings by omitting the upper and lower fairing surfaces. This omission eliminates the need for many of the mechanisms associated with collapsing and stowing the fairing assembly. These simplified fairings, however, must still be carefully designed to ensure that they do not interfere with the full movement of the trailer doors. Accordingly, most partial fairing designs feature flat panels which are mounted to the trailer doors or the hinges of the doors to enable the fairings to be collapsed flat against the door when the fairing is not in use or when the door is opened. Unfortunately, due to the geometry of typical swinging trailer doors, these flat panel designs inherently feature abrupt angular transitions and/or gaps between the sides of the trailer and the fairing surfaces. A recent attempt to remove these discontinuities uses pliable panels which are hinged at the sides of the trailer rather than at the trailer doors (U.S. Pat. No. 6,854,788 to Graham). These panels are flat when not deployed but are pliable enough to be bent or pulled into a smooth contoured aerodynamic shape when the trailer doors are closed. Unfortunately, these pliable fairings inherently exert a pulling force on the trailer doors as the doors are opened and closed. This added resistance is undesirable because it encumbers the operation of the trailer doors.